Field of the Invention
The present invention relates to an image display apparatus and a control method therefor.
Description of the Related Art
Heretofore, when X ray films obtained by photographing with X rays or the like were interpreted, the films were placed on a film viewer to be interpreted. Recently, with the digitalization of medical images, a monitoring diagnosis using an image display apparatus (medical viewer) has become mainstream, and some medical institutions do not possess a film viewer, as the filmless operation becomes more popular. Additionally, medical image display apparatuses having a function of using the (digital) display apparatus body as a film viewer by making a backlight emit light with high brightness and performing white display on a liquid crystal panel are beginning to be widely used. By using such a medical image display apparatus, not only the interpretation of digital images but also the interpretation of film images is possible with a single medical image display apparatus, which improves the convenience. On the other hand, there has been a problem, even since the age of film interpretation using a film viewer, in that a region where light is emitted with high brightness (hereinafter referred to as a film viewer region) is larger than the area of the film, potentially causing glare or otherwise affecting the viewer, whereby an erroneous diagnosis is caused or interpretation efficiency is lowered. This problem exists also in medical image display apparatuses having a film viewer function.
Japanese Patent Application Laid-open No. H2-13920 discloses a technology of measuring the quantity of light that enters from the outside of an image display apparatus, while mechanically vertically moving a linear photosensor provided in the apparatus, to determine a region (film region) where a film is placed, and matching an emission area with the film region. Additionally, Japanese Patent Application Laid-open No. 2000-241749 discloses a technology of detecting a film region by sandwiching a pressure sensor and a film in a clip member, or a technology of detecting a film region by pressing four corners of a film that is set in a monitor by using a touch panel.